This invention relates to high pressure sealing joints and more particularly to a seal assembly for sealing a fluid control line connection between coaxially aligned flow passages in adjoining members, such as between a tubing hanger and a tubing head adapter in a wellhead.
There is a variety of downhole tools and devices employed in well operations which rely on fluid control lines for their operation. For example, one of the primary means of preventing blowouts in producing wells is by the use of surface controlled subsurface safety valves. These valves are normally set several hundred feet below the surface in the tubing string and can be either wireline or tubing retrievable types. These downhole safety valves require the installation of hydraulic control lines for opening and closing operations. This invention relates to a seal assembly in an installation for bringing control line fluid pressure from the surface controls through the tubing head adapter and the tubing hanger for coupling to the control line which extends downwardly to a connection on the downhole device such as a subsurface safety valve. Heretofore, sealing has been accomplished in the passage between the tubing hanger and tubing head adapter by means of seals which rely primarily on elastomeric sealing elements. These are generally inadequate under high pressure and high temperature conditions and in critical service hydrogen sulfide or carbon dioxide environments. Some seals are pressure energized as determined by their design and relationship with the elements which are connected, but these generally, rely on internal pressurization. In the application of sealing the control line passage between the tubing head adapter and the tubing hanger it is important that a fluid-tight seal be achieved whether fluid pressure be applied from the interior or the exterior of the joint.
The present invention has, as its primary object, the provision of a seal assembly for sealing the passage in a fluid control line connection between a tubing head adapter and a tubing hanger under high pressure and high temperature conditions and in critical service corrosive environments.
Another object is to provide a seal assembly for sealing the passage of a pneumatic or hydraulic control line through a tubing head adapter and a tubing hanger by means of a metallic tubular sealing element having tapered frusto-conical end portions which are receivable in opposed pockets formed in aligned adjoining flow passages in the tubing head adapter and tubing hanger and which are subject to deformation to effect metal-to-metal seals with frusto-conical seating surfaces in the opposed pockets when the tubular sealing element is subjected to an axial compression by bolting together of the tubing head adapter and the tubing hanger.